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Aug- 30, 1932- l. BRANTHWAITE 1,874,235

ELECTR IC CONDUCTOR Filed April 10. 1929 A TTORNEYS.

Patented Aug. 30, 1932 UNITED STATES PATENT ori-ICE ISAAC BRANTHWAITE, 0F PASSAIC, NEW JERSEY, ASSIGNOB TO THE OKONITE-CALLEN- DEB CABLE COMPANY, INCORPORATED,

TION OF NEW JERSEY Application illed April 10,

The present invention relates to an improvement in electric conductors for the transmission of power, and has for one of its objects the provision in a stranded conductor structure of a construction for increasing the eficien'cy of the conductor by locating most advantageously the area of cross section for the-flow of oil alon the core of the conductor, and increasing t e surface area for the flow of oil from the core through the strands.

In the use of electric conductors for the transmission of power, the size of conductor which is required to carry the current may have a diameter which is smaller than is advisable for the voltage on the cable, owing tothe fact that the electric stresses on the surface of the conductor may become very high so that the insulation surrounding the conductor may in time weaken and fail electrically on account of what is known as overstressing. Also, in the case of im regnated paper cables it is quite essential that means be provided for maintainin the paper insulation thoroughly filled wit oil at all times if the cable is to operate eiciently the desired length of time.

Various expedients have been tried for reducing the electric stresses to a minimum and for maintaining sufficient oil in the paper insulation.

For example, in an endeavor to keep the electric stresses on the surface of the conductor to a minimum, conductors have been constructed employing a solid core of ro or built up paper insulation about which t e stranded conductors composing the conductor are laid, Such a construction is of no aid so far as maintaining the paper insulation surrounding the conductors filled with oil is concerned.

Again, with a view to maintaining the insulation filled with oil, a hollow core has been suggested, this core functioning as an oil channel, and comprising a spiral coil forming a support for the stranded conductors laid about the same. In such construction the diametcrof the hollow core is a function of the cross sectional area of the co per strands in the conductor and the .desir diand for OF PATEBSON, NEW JERSEY, A CORPORA- ELECTBIC CON DUCTOB 1929. Serial No. 353,921.

ameter over the strands, and when this hollow core functions as a channel for the flow of oil along the conductor and for the flow of oil from the channel through the strands surrounding the same and into the insulation a certain area of cross section is obtained for the flow of oil along the conductor, which area isy dependent non the diameter ofthe hollow core. g A certain surface area is also obtained for the flow of oil from the hollow core through the strands, this latter being a function ofthe circumference of the circle madeY by the core.

The present invention provides a construction wherein the surface areaA for the flow of oil from the core through the strands is increased, as compared with the hollow core type of conductor above referred to, thereby increasing the eiciency'of the conductor. This construction also provides the necessary diameter of conductor for reduction of electric stresses on the surface of the conductor, and a freer flow of oil along and between the -strands of the conductor.

In the drawing:

Fig. 1 is a partial perspective of a conductor constructed in accordance with my invention; and

Figs. 2 and 3 are views of a modification.

Referring first of all to Fig. 1, my construction embodies two sets of stranded conductors 1 and 2, collectively` providing the desired conductor area or area of conductor. Theyvneed not be of equal cross Asection and the outer set may comprise but a single layer, while the inner set comprises a plurality of layers. In constructing such a conductor, the desired outside diameter of the conductor and the most suitable size of strands for the outer set 2 are determined and the sum of the conductor areas of these strands computed. The difference between this sum and the desired area of conductor gives the necessary conductor area of the inner set of stranded conductors. Knowing the conductor area of this inner set of conductors its diameter is readily determined.

This results in a structure in which the inside diameter of the outer conductor set or section 2 is greater than the outside diameter of the inner conductor 'set or section 1,' thereby providing a space, which, if the two sets of. conductors 1 and 2- could be maintained separated, would permit of the iiow of oil therethrough.

To maintain this separation I employ in one instance a fluted metal spacer 3 surrounding the inner conductors 1 and lying intermediate the inner and outer conductor sets or sections in the space above mentioned. This spacer may be made by forming a lead sheath about the inner conductors 2, providing this sheath with flutes or projections 4, these projections 4 together with the strands 5 of thev outer conductor set 2 forming channels designated 6, for the iow of oil along` the conductor, and from these channels between the strands'or conductors 5 into the insulation 7 surrounding the conductors. The total or collective surface area of the channels 6 exceeds that of a hollow core conductor such as above referred to having the same conductor area.

8 is the usual lead sheath employed in powf er conductors and may, if desired, be provided with projections to contact with thel outer surface of the insulation 7 thereby providing' channels for the iow of oil along the sheath.

In Fig. 3 I have modified somewhat the construction above described by substituting4 the member 4 with a member 9 wound spirally about the inner conductors 1. This construction has the same characteristics as compared with a hollow core conductor as those referred to in connection with my description of Fig. l, with the ladditional feature of pery mitting of a iow of oil along and in contact with the conductor set or section 1 and radially inwardly between the strands of this set of conductors.

What I claim is f In an electric conductor, the combination of an'inner set and an outer set of stranded conductors concentrically disposed and collectively providing the cross sectional area necessary for the desired current transmission, an insulating` medium, an externally iuted continuous sheath over the inner set of conductors, and lying; in the space between the two sets of conductors, said external flutes serving as channels for the How of the insulating medium alongB and between the strands of the outer set of conductors.

This speciication signed' this 6th day of April, 1929.

` ISAAC BRANTAITE. 

